This invention relates to a conveying arm that can be miniaturized and that is superior in characteristics of control.
Conventionally, when a semiconductor substrate such as a semiconductor wafer (that can be abbreviated to xe2x80x9cwaferxe2x80x9d) is conveyed between a cassette that can accommodate the wafer and a semiconductor manufacturing unit or between various semiconductor manufacturing units, a conveying arm that forms a conveying unit is used.
A multi-chamber type of processing unit is explained as an example, which is also a cluster type of unit. In the case, a conveying arm is accommodated in a transfer-chamber (common transfer-chamber). The conveying arm has a substrate holding portion. The substrate holding portion is formed in such a manner that the substrate holding portion can be moved into not only the transfer-chamber but also various process-chambers or a cassette-chamber that are connected to the transfer-chamber. Thus, when the conveying arm is operated, an unprocessed wafer can be conveyed from a cassette in the cassette-chamber to any of the process-chambers through the transfer-chamber. In addition, when the conveying arm is operated, a processed wafer can be conveyed back from any of the process-chambers to the cassette through the transfer-chamber.
As the conveying arm, a scalar-type of conveying arm and a frog-leg type of conveying arm are used in general.
The scalar-type of conveying arm has two or more arms that connect a substrate holding portion and a pivotable shaft. A pivoting mechanism is connected to the pivotable shaft and respective pivotable portions of the arms, for example via one or more rotating belts and one or more pulleys. Thus, when the pivotable shaft is operated, the arms can extend or retract in a horizontal direction and the substrate holding portion can be moved to predetermined positions.
On the other hand, the frog-leg type of conveying arm has a plurality of frog-leg arms, each of which consists of a pair of arms that are connected with each other substantially in a frog-leg manner. The plurality of frog-leg arms connects a substrate holding portion and a pivotable shaft. A pivoting-power transmitting mechanism is connected to the pivotable shaft. When the pivotable shaft is operated, the plurality of frog-leg arms can extend or retract in a radial direction from a center of the pivot and the substrate holding portion can be moved to predetermined positions.
When the scalar type of conveying arm is adopted for the above processing unit, the rotating belts and the pulleys, which form the pivoting mechanism, have to be disposed in the transfer-chamber through which the wafer is moved. Thus, when the conveying arm is operated, particles may tend to be generated. The particles may easily contaminate the wafers and may deteriorate a yield of the wafers.
In addition, in the scalar type of conveying arm, vibrations may tend to be generated because the scalar type of conveying arm has the rotating belts and the pulleys. Thus, it is difficult to raise a conveying speed.
When the frog-leg type of conveying arm is adopted for the above processing unit, the above rotating belts or pulleys generally need not be disposed in the transfer-chamber. Thus, it can be prevented or inhibited that particles are generated and that vibrations are generated. Thus, it is possible to raise a conveying speed.
However, because of the structure itself of the frog-leg type of conveying arm, an end portion of the arms connected to the substrate holding portion can not retract in a radial direction of a side substantially opposite to the substrate holding portion with respect to the center of the pivot of the whole conveying arm. That is, there is a limitation to enlarge an extending/retracting distance, in which the conveying arm can extend and retract, with respect to a pivoting radius of the conveying arm. Thus, when the center of the pivot is away from a position to which a wafer should be moved, the conveying arm has to be proportionally enlarged. Therefore, it is impossible that the unit adopting the conveying arm is miniaturized.
In addition, if the substrate holding portion is arranged further away from the center of the pivot, the substrate holding portion is subjected to a larger centrifugal force when the conveying arm is pivoted. Thus, because of the centrifugal force and/or vibrations caused by the centrifugal force, the wafer placed on the substrate holding portion may be moved out from a predetermined position or may even fall down.
In addition, in both of the scalar type of conveying arm and the frog-leg type of conveying arm, a resolution in a state wherein the conveying arm relatively contracts is very different from a resolution in another state wherein the conveying arm relatively extends. That is, when the conveying arm is caused to extend or contract in the state wherein the conveying arm relatively contracts, a resolution by which the substrate holding portion is moved in a radial direction is relatively high. On the other hand, when the conveying arm is caused to extend or contract in the state wherein the conveying arm relatively extends, a resolution by which the substrate holding portion is moved in the radial direction is relatively low. Thus, it is difficult to exactly convey a wafer placed on the substrate holding portion to a predetermined position. In particular, if the conveying arm is operated at a higher speed, it becomes more difficult to precisely convey the wafer.
This invention is intended to solve the above problems in the prior art. The object of this invention is to provide a new and improved conveying arm in which an extending/retracting distance with respect to a pivoting radius of the conveying arm is large and a resolution in a state wherein the conveying arm relatively contracts is substantially the same as a resolution in another state wherein the conveying arm relatively extends.
In order to achieve the above object, a conveying arm according to the invention comprises: a first pivotable shaft; a first arm having a one-side end portion connected to the first pivotable shaft; a third arm having an intermediate pivotable portion and a one-side end portion pivotably connected to an other-side end portion of the first arm; a fifth arm having a one-side end portion pivotably connected to an other-side end portion of the third arm; a second pivotable shaft; a second arm having a one-side end portion connected to the second pivotable shaft; a fourth arm having an intermediate pivotable portion pivotably connected to the intermediate pivotable portion of the third arm and a one-side end portion pivotably connected to an other-side end portion of the second arm; a sixth arm having a one-side end portion pivotably connected to an other-side end portion of the fourth arm; and a seventh arm having a holding portion for an object to be conveyed, pivotably connected to an other-end portion of the fifth arm and an other-end portion of the sixth arm; wherein a positional relationship between the one-side end portion of the third arm, the intermediate pivotable portion of the third arm and the other-side end portion of the third arm is in such a manner that a line linking the one-side end portion to the intermediate pivotable portion is substantially perpendicular to a line linking the other-side end portion to the intermediate pivotable portion, and a positional relationship between the one-side end portion of the fourth arm, the intermediate pivotable portion of the fourth arm and the other-side end portion of the fourth arm is in such a manner that a line linking the one-side end portion to the intermediate pivotable portion is substantially perpendicular to a line linking the other-side end portion to the intermediate pivotable portion.
As another feature of the invention, the other-side end portion of the third arm and the other-side end portion of the fourth arm are in a same side as the first pivotable shaft and the second pivotable shaft with respect to the respective intermediate pivotable portions.
Preferably, the third arm and the fourth arm have shapes substantially symmetric with respect to each other. In particular, it is preferable that the third arm and the fourth arm are substantially L-shaped arms.
In addition, it is preferable that the first arm and the second arm have a substantially same length. In addition, it is preferable that the fifth arm and the sixth arm have a substantially same length.
If the first pivotable shaft and the second pivotable shaft are adapted to be independently pivoted around a same axis, a pivoting movement of the holding portion for an object to be conveyed can be achieved by pivoting the first pivotable shaft and the second pivotable shaft in a same direction. In addition, in the case, a linear movement of the holding portion for an object to be conveyed can be achieved by pivoting the first pivotable shaft and the second pivotable shaft in opposite directions.
If the first pivotable shaft and the second pivotable shaft are adapted to be pivoted around separate axes, the first pivotable shaft and the second pivotable shaft are adapted to be pivoted in opposite directions through a same angle. In addition, preferably, the first pivotable shaft and the second pivotable shaft are provided on a driving mechanism that can pivot the whole conveying arm.
In addition, the fifth arm and the sixth arm are adapted to be pivoted with respect to the seventh arm in such a manner that an angle formed by the fifth arm and the seventh arm is always equal to an angle formed by the sixth arm and the seventh arm.
In addition, in order to achieve the above object, another conveying arm according to the invention comprises: a guide extending in a substantially straight manner; a first slider and a second slider that can slide along the guide; a third arm having an intermediate pivotable portion and a one-side end portion pivotably connected to the first slider; a fifth arm having a one-side end portion pivotably connected to an other-side end portion of the third arm; a fourth arm having an intermediate pivotable portion pivotably connected to the intermediate pivotable portion of the third arm and a one-side end portion pivotably connected to the second slider; a sixth arm having a one-side end portion pivotably connected to an other-side end portion of the fourth arm; and a seventh arm having a holding portion for an object to be conveyed, pivotably connected to an other-end portion of the fifth arm and an other-end portion of the sixth arm; wherein a positional relationship between the one-side end portion of the third arm, the intermediate pivotable portion of the third arm and the other-side end portion of the third arm is in such a manner that a line linking the one-side end portion to the intermediate pivotable portion is substantially perpendicular to a line linking the other-side end portion to the intermediate pivot able portion, and a positional relationship between the one-side end portion of the fourth arm, the intermediate pivotable portion of the fourth arm and the other-side end portion of the fourth arm is in such a manner that a line linking the one-side end portion to the intermediate pivotable portion is substantially perpendicular to a line linking the other-side end portion to the intermediate pivotable portion.
In the case, a movement of the holding portion for an object to be conveyed in a direction parallel to the guide can be achieved by moving the first slider and: the second slider in a same direction, and a movement of the holding portion for an object to be conveyed in a direction substantially perpendicular to the guide can be achieved by moving the first slider and the second slider in opposite directions.
In the above intention as well, as another feature, the other-side end portion of the third arm and the other-side end portion of the fourth arm are in a same side as the guide with respect to the respective intermediate pivotable portions.
In the above invention as well, preferably, the third arm and the fourth arm have shapes substantially symmetric with respect to each other. In particular, it is preferable that the third arm and the fourth arm are substantially L-shaped arms. In addition, it is preferable that the first arm and the second arm have a substantially same length. In addition, the fifth arm and the sixth arm are adapted to be pivoted with respect to the seventh arm in such a manner that an angle formed by the fifth arm and the seventh arm is always equal to an angle formed by the sixth arm and the seventh arm.
According to the invention, an end portion of the seventh arm in a side of the fifth arm and the sixth arm can be moved over a center of the pivot of the conveying arm, that is, can retract over the center of the pivot in a direction substantially opposite to an extending direction of the holding portion for an object to be conveyed. Thus, an extending/retracting distance of the conveying arm can be enlarged without increasing a pivoting radius of the conveying arm. Thus, the conveying arm can be miniaturized, and a unit accommodating the conveying arm can be miniaturized.
In addition, when the conveying arm is caused to retract, a center of the holding portion for an object to be conveyed and the center of the pivot of the conveying arm can be substantially equal or close to each other. Thus, even when the conveying arm is pivoted while an object to be conveyed is mounted on the holding portion for an object to be conveyed, the object to be conveyed may not be subjected to a too large centrifugal force. Thus, it can be prevented that the object to be conveyed is moved out from a prescribed position on the holding portion for an object to be conveyed or that the object to be conveyed falls down from the holding portion for an object to be conveyed.
In addition, since the third arm and the fourth arm whose intermediate pivotable portions are connected with each other are adopted, a resolution of the movement (an extending/contracting rate) of the conveying arm in a state wherein the conveying arm relatively contracts may be substantially equal to a resolution of the movement in another state wherein the conveying arm relatively extends. Thus, wherever the holding portion for an object to be conveyed is arranged, it may become easy to exactly convey an object to be conveyed placed on the holding portion for an object to be conveyed to a predetermined position. In addition, even if the conveying arm is operated at a higher speed, operational performance of the conveying arm may not be deteriorated and the conveying arm can be controlled easily and surely.